Eccentric pin bearing

ABSTRACT

In a preferred embodiment, a trunnion-type piston pin is eccentrically received in the cylindrical bore of a piston member having bifurcated arms encircling and engaging the lower side of the piston pin. An arcuate bearing segment is received in a saddle portion of the piston member bore between it and the piston pin to transfer combustion loads therebetween. The bearing segment is of varying thickness having arcuate inner and outer surfaces formed on the centers of and engaging the surfaces of the piston pin and piston member bore, respectively. The arrangement permits provision for a partial insert bearing using a cylindrical piston pin bore and piston pin for simplicity of manufacture. Simple means for securing the bearing segments in the saddle portion and other features are provided.

United States Patent [1 1 Sihon I [451 Feb. 5, 1974 1 ECCENTRIC PINBEARING 639,570 6/1950 Great Britain 308/237 75 Inventor: Tanas M.Sihon, Ypsilanti, Mich.

73 Assi nee: General Motors Co ration Examiner lrwin Cohen 1 g DetroitMich rpo Attorney, Agent, or Firm-Robert J. Outland [22] Filed: Feb. 28,1972 [21] Appl. No.: 229,695 [57] ABSTRACT In a preferred embodiment, atrunnion-type piston pin [52] US. Cl 92/187, 92/238, 308/2, iseccentricany received in the cylindrical bore of a I t Cl piston memberhaving bifurcated arms encircling and f J C engaging the lower side ofthe piston pin. An arcuate [58] new of Search" 308/2 237; 92/187 bearingsegment is received in a saddle portion of the 92/238; 287/20 P pistonmember bore between it and the piston pin to transfer combustion loadstherebetween. The bearing [56] References C'ted segment is of varyingthickness having arcuate inner UNITED STATES PATENTS and outer surfacesformed on the centers of and en- 212,665 2/1879 Defreest 308/237 xgaging the surfaces of the piston pin and piston mem- 1,341,938 6/1920Shoemaker... 308/237 ber bore, respectively. The arrangement permitspro- 2,433,765 1949 Hflmel 308/237 X vision for a partial insert bearingusing a cylindrical 3,053,595 911962 Dilworth.... 92/216 piston i b reand piston pin for simplicity of manuw f g 7 2 facture. Simple means forsecuring the bearing seg- I 1 iams 3,555,972 1 1971 Hulsing 92 190 x2325 the saddle porno and features are pro FOREIGN PATENTS ORAPPLICATIONS 895,694 4/1944 France. 308/237 5 Claims, 2 DrawingFigures 1t 1 a i Z8 1 a y fly Q 52 C X a 1/ T; .fi

, x j az t 65 1 ECCENTRICI PIN BEARING FIELD OF THE INVENTION m'ernber.More specifically, the invention relates to trunnion-type piston pinconnections involving the use of an insert bearing segment.

BACKGROUND OF THE INVENTION It is known in the art relating to pinbearings wherein the major loads are carried in one direction betweentwo connected members to provide a bearing insert segment which acts totransmit the loads in the primary load direction, while direct contactbetween the load transmitting parts is used to transmit minor loads inother than the primary direction.

Such prior art arrangements are exemplified by US. Pat. Nos. 3,476,021Williams and 3,555,972 Hulsing, both assigned to the assignee of thepresent invention. These patents disclose somewhat different types ofpiston constructions, both of which use a so-called trunnion-type pistonpin connection wherein a piston pin, nonmovably secured to an engineconnecting rod, is oscillatably retained within the transverse bore of amajor load carrying member-of a piston assembly.

In each case, a separate bearing segment is retained within the pistonmember and engaged by the piston pin so as to carry the major thrustloads acting between the piston and piston pin. Transmission of loads inthe opposite direction is accomplished by direct contact between thepiston pin and its associated piston member, which includes portionsthat encircle the opposite ends of the piston pin adjacent the ends ofthe connecting rod.

Such constructions as are shown in the abovementioned patents areparticularly adapted for use in two-cycle engines wherein the loadsacting on the piston and connecting rod assembly are primarilycompressive in nature. However, such arrangement could equally well beused in other machines, such as compressors orthe like where the primaryloading is in one direction between the connected members.

In the prior art, such as that previously described, the use of anarcuate bearing segment rather than a full bearing sleeve has resultedin the need to provide a transverse pin receiving opening which, ratherthan being a true cylindrical bore, is formed .with a recess along oneside sufficiently deep to provide for the insertion of the bearingsegment, which is commonly known in this instance as an insert. Theprovision of the recess for the bearing insert complicates the manu-SUMMARY ,OF THE INVENTION The present invention provides a pin bearingconstruction which may be used in piston pin assemblies or otherappropriate bearing locations. This construction provides for the use ofa segmental bearing insert in an arrangement that eliminates the needfor provision of a special recess to receive the insert in thetransverse bore of the pin receiving member and thereby eliminates therequirement of broaching 'or other special machining operations in themanufacture of the pin bearing assembly.

Pin bearing constructions according to this invention involve theprovision of a cylindrical bore in the pin receiving member which issubstantially larger than the diameter of the mating cylindrical wristpin, which may be of the trunnion type or some other known arrangementof gudgeon or wrist pin. The wrist pin is located eccentrically withinthe bore with its clearance substantially taken up in the unloaded orlightly loaded direction of the assembly. 'An arcuate bearing segmentinsert is provided between the pin and the wall of the bore of the pinreceiving member in the path of trans mission of the heavy load forcesthrough the assembly. The bearing insert is of varying thickness beinggenerally thickest at its center and thinner toward its ends so that itsubstantially fills the clearance space between the eccentricallydisposed piston pin and bore. In this position, the insert is arrangedwith its convex arcuate inner surface centered onthe axis of the pistonpin and its concave arcuate outer surface centered on the axis of thepin receiving member bore.

In order'to retain the bearing insert in position in the bore of the pinreceiving member, a pair of small recesses may be provided which arepreferably located about the center of the length of the bearing insertwith one at each of its edges so as to receive slightly de-, formedportions of the bearing edges to retain the insert in position.

These and other features and advantages of the invention will be morefully understood from the following description of a preferredembodiment taken together with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a transverse cross-sectional view of a piston-connecting rodassembly having pin bearing means according to the invention, the viewbeing taken in the plane transverse to the axis of the piston pin; and

FIG. 2 is a cross-sectional view of the assembly of FIG. 1 taken in aplane along the axis of the piston pin DESCRIPTION OF THE PREFERREDEMBODIMENT Referring now to the drawing in detail, numeral 10 generallyindicates a piston-connecting rod assembly of the type having pinbearing means according to the invention. In the present instance, thepiston is of the crosshead type construction disclosed in the previouslymentioned U. S. Pat. No. 3,555,972 Hulsing. However, it shouldbe'understood that the pin bearing arrangement of this invention mightequally well be used in numerous other types of piston and othercomponent constructions.

The piston of assembly 10 includes separate head and skirt members 12and 14, respectively, which are maintained in assembly by atrunnion-type piston pin 16 secured to a connecting rod 18 of aninternal combustion engine.

The head member 12 of the piston assembly includes a recessed crownportion 20 connected at its perimeter with the depending wall portion 22which forms a ring belt having a plurality of compression ring grooves24. The lower end of wall portion 22 is reduced in diameter and isprovided with an external annular groove 26 in which there is carried aseal ring 28 for a purpose to be subsequently described.

The crown and wall portions 20, 22 of the head member are connectedthrough struts or columns 30 with a piston pin connecting portion 32that includes a central saddle portion 34 terminating'laterally in apair of bifurcated arms 36. A generally cylindrical bore 38 extendslaterally through the saddle portion and bifurcated arms forming a pairof pin-receiving openings 40 through the arms with a downwardly facingarcuate recess 42 in the saddle portion intermediate the arms 36.

Within the upper portion of the bore 38 there is received an arcuatebearing segment insert 44 which extends laterally the length of thesaddleportion, engaging the downwardly facing surfaces of the saddleportion arcuate recess 42 and the upper portions of the pin receivingopenings 40 which make up the pin receiving bore 38. Bearing segment 44is generally thicker at its center and thinner toward its edges, beingformed with a convex arcuate outer surface and a concave arcuate innersurface which are formed on different axes, as will be subsequently morefully described.

Piston pin 16 is received within transverse bore 38 engaging the concaveinner surface of the bearing insert along the piston pin s surfaces. Thelower surface of the pin 16 extendstinto close proximity with the lowerportions of the bore 38 in pin receiving openings 40 with a slightworking clearance therebetween, but capable of making linear contactwith the walls of the bore in the bifurcated arms 36. The ends of thepin are hollowed out to reduce weight. However, the central portion issolid and is provided with a pair of angled threaded holes 46 which areengaged by bolts 48 that cooperate with spacers 50 to secure theconnecting rod 18 to the piston pin 16. The rod 18 is secured to the pinintermediate arms 36 and acts to maintain the assembly together. An oilpassage 52 in the connecting rod is aligned with a connecting passage 54through the piston pin which in turn connects through an opening 56 inthe bearing insert with a connecting opening 58 in the piston membersaddle to provide a path for piston cooling oil to be supplied to thepiston interior.

The ends of the piston pin 16 extend beyond the saddle portion andbifurcated arms of the piston member and are received within cylindricalopenings 60 provided in bosses 62 of the piston skirt 14. The outer endsof these openings are provided with closure plates 64 to prevent theescape of lubricating oil from the piston interior.

The skirt member is adapted to absorb substantially all the side thrustforces applied to the piston during movement of the connecting rodthrough the supporting connection between the piston pin and the skirtboss openings. The lower portion of the skirt is provided with oil ringgrooves 66 while the upper portion includes an upward annular extension68 which surrounds the reduced diameter portion of the piston memberring belt wall 22 and is engaged by the seal ring 28 so as to preventthe escape of cooling oil from the piston interior to the externalwalls.

Adjacent the edges of the bearing insert 44 and approximately centeredintermediate its ends, two short angular recesses 70 are provided in theotherwise arcuate surface of the saddle portion recess 42 which receivesthe bearing segment 44. At these points, short lengths of the bearingwall edges are deformed, as at 72 so as to extend into the recesses 70and maintain the insert bearing in position in the head member saddleportion. While the portion 72 may be deformed into position uponassembly, it is preferable that the bearing be preformed to its finalshape so that the insert may be merely snapped in place during assemblyto be retained thereafter by the cooperation of the deformed portion 72with the recesses 70.

With the arrangement as described, it is noted that the openings 60 inthe piston skirt have an axis which is substantially the same as that ofthe piston pin 16 and which is also the axis of the convex inner surfaceof the insert bearing 44 as it is installed in the assembly. Thetransverse bore 38 which extends through arms 36 and saddle portion 34of the piston member has, however, an axis spaced slightly above that ofthe. piston pin since the piston pin is located eccentrically of thebore 38, having the lower surface of the piston pin in or near contactwith the lower surface of the bore 38 in the bifurcated arms 36. Aspreviously mentioned, the space between the upper surface of the pistonpin and the saddle portion recess is filled by the bearing insert 44,the upper surface of which conforms to the saddle portion recess andaccordingly shares an axis with the bore 38. i

The result of the above construction is that manufacture of the pistonassembly is simplified, since the opening 38 in which the piston pin andbearing insert are located may be formed by a simple boring opera tion,thus avoiding the need for broaching or other more complicated machiningoperations utilized in the prior art arrangements. The recesses 70 bywhich the insert 44 is maintained in an installed position may beprovided by simple milling operations resulting in a less expensive andsimplified manufacturing procedure for the complete assembly. The mannerof retaining the piston pin to the connecting rod is also simplifiedover certain of the prior art constructions.

While the invention has been described by reference to a preferredembodiment showing the application of the pin bearing assembly to aso-called crosshead type piston, it should be recognized that theinventive concepts disclosed are applicable in numerous otherconstructions where a pin bearing may be utilized. Accordingly, it isdesired that the invention not be limited by the specific arrangementdisclosed, but that the invention be given its full scope as permittedby the language of the following claims.

I claim:

1. In an oscillating pin bearing construction for transmitting forcesbetween a piston and a connecting rod,

a first member having a cylindrical bore therein,

an arcuate bearing member retained along one side of said bore and inload transmitting relation therewith, and

a cylindrical pin member eccentrically disposed in 3. The assembly ofclaim 2 wherein said piston memsaid bore and in load transmittingrelation with her includes a pair of recesses in the bore portions atsaid bearing member, said pin member being of the arcuately oppositeedges of said bearing segment, sufficient diameter to fill thetransverse dimension said segment edges having deformed portionsreceived of said bore between said bearing member and the 5 within saidrecesses to retain said segment in position opposite side of said bore,except for operating in said bore. clearance, 4. A piston assembly foran internal combustion ensaid bearing member having a cylindrical convexgine, said assembly comprising outer surface mating with and in opposedload a piston member having a pin receiving portion intransmittingrelation to the surface of said bore 10 eluding a central saddle portionwith bifurcated and centered on theaxis thereof and said bearing armsextending therefrom and a transverse cylinmember having a cylindricalconcave inner surface drical bore through said arms and saddle portionmating with and in opposed load transmitting relaforming pin receivingopenings in said arms and a tion to the surface of said pin member andcencoaxial recess in said saddle portion intermediate tered on the axisthereof, 5 said arms,

whereby loads in one direction between said pin acylindrical pinreceived in said piston member bore member and said first member aretransmitted and extending into both said pin receiving openthrough saidbearing member, while loads in the ings, said pin being of substantiallysmaller diameopposite direction are transmitted through direct ter thansaid bore and being eccentrically disposed contact between said firstmember and said pin therein with the clearance being largely taken upmember. on the side of said openings away from the coaxial 2. A pistonpin bearing assembly for an internal comrecess of said saddle portion,and

bustion engine, said bearing assembly comprising an arcuate bearingsegment disposed in said bore a piston member having a load transmittingportion and engaging the inner surface of said bore and the with acylindrical bore therein, outer surface of said piston pin, said bearingsega cylindrical piston pin eccentrically disposed in said ment being ofvarying thickness to conform to the bore and in load transmittingengagement with the clearance space between the eccentrically diswallthereof at one position of the circumference posed surfaces of said pinand bore. of said bore, and 5. The assembly of claim 4 and furthercomprising an arcuate bearing segment extending between said aconnecting rod secured to said pin intermediate said pin and said borewall at points generally opposite bifurcated arms and maintaining saidpin in assembly the position of engagement between said pin and withsaid piston member, and

said bore wall, said bearing segment having a convex outer surface inload transmitting engagement with said bore wall and centered on theaxis thereof and said bearing segment having a concave inner surface inload transmitting engagement with said locking recesses formed in thecylindrical surface of said bore, said bearing segment havingcooperating deformations at its arcuately opposite edges, en-

gaging said locking recesses to retain said bearing segment within saidbore.

pin and centered on the axis thereof.

1. In an oscillating pin bearing construction for transmitting forcesbetween a piston and a connecting rod, a first member having acylindrical bore therein, an arcuate bearing member retained along oneside of said bore and in load transmitting relation therewith, and acylindrical pin member eccentrically disposed in said bore and in loadtransmitting relation with said bearing member, said pin member being ofsufficient diameter to fill the transverse dimension of said borebetween said bearing member and the opposite side of said bore, exceptfor operating clearance, said bearing member having a cylindrical convexouter surface mating with and in opposed load transmitting relation tothe surface of said bore and centered on the axis thereof and saidbearing member having a cylindrical concave inner surface mating withand in opposed load transmitting relation to the surface of said pinmember and centered on the axis thereof, whereby loads in one directionbetween said pin member and said first member are transmitted throughsaid bearing member, while loads in the opposite direction aretransmitted through direct contact between said first member and saidpin member.
 2. A piston pin bearing assembly for an internal combustionengine, said bearing assembly comprising a piston member having a loadtransmitting portion with a cylindrical bore therein, a cylindricalpiston pin eccentrically disposed in said bore and in load transmittingengagement with the wall thereof at one position of the circumference ofsaid bore, and an arcuate bearing segment extending between said pin andsaid bore wall at points generally opposite the position of engagementbetween said pin and said bore wall, said bearing segment having aconvex outer surface in load transmitting engagement with said bore walland centered on tHe axis thereof and said bearing segment having aconcave inner surface in load transmitting engagement with said pin andcentered on the axis thereof.
 3. The assembly of claim 2 wherein saidpiston member includes a pair of recesses in the bore portions at thearcuately opposite edges of said bearing segment, said segment edgeshaving deformed portions received within said recesses to retain saidsegment in position in said bore.
 4. A piston assembly for an internalcombustion engine, said assembly comprising a piston member having a pinreceiving portion including a central saddle portion with bifurcatedarms extending therefrom and a transverse cylindrical bore through saidarms and saddle portion forming pin receiving openings in said arms anda coaxial recess in said saddle portion intermediate said arms, acylindrical pin received in said piston member bore and extending intoboth said pin receiving openings, said pin being of substantiallysmaller diameter than said bore and being eccentrically disposed thereinwith the clearance being largely taken up on the side of said openingsaway from the coaxial recess of said saddle portion, and an arcuatebearing segment disposed in said bore and engaging the inner surface ofsaid bore and the outer surface of said piston pin, said bearing segmentbeing of varying thickness to conform to the clearance space between theeccentrically disposed surfaces of said pin and bore.
 5. The assembly ofclaim 4 and further comprising a connecting rod secured to said pinintermediate said bifurcated arms and maintaining said pin in assemblywith said piston member, and locking recesses formed in the cylindricalsurface of said bore, said bearing segment having cooperatingdeformations at its arcuately opposite edges, engaging said lockingrecesses to retain said bearing segment within said bore.